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import argparse
import sys
from typing import List

from code_formatter import code_formatter


def parse_args():
    parser = argparse.ArgumentParser()
    parser.add_argument("hh", help="the path of the debug flag header file")
    parser.add_argument("name", help="the name of the debug flag")
    parser.add_argument("desc", help="a description of the debug flag")
    parser.add_argument(
        "fmt", help="whether the flag is a format flag (True or False)"
    )
    parser.add_argument(
        "components",
        help="components of a compound flag, if applicable, joined with :",
    )
    args = parser.parse_args()
    return args


def write_header_file(
    hh: str, name: str, desc: str, fmt: bool, components: List[str]
):
    """
    Generates the C++ header file for a debug flag.

    This function creates a C++ header that defines a debug flag, which can be
    either a simple flag or a compound flag composed of other flags. The
    generated header uses unions to ensure that debug flag objects are not
    destructed, allowing them to be used safely even in the destructors of
    other objects.

    Args:
        hh: The path to the header file to generate.
        name: The name of the debug flag.
        desc: A description of the debug flag.
        fmt: A boolean indicating whether the flag is a format flag.
        components: A list of component flag names for a compound flag.
    """
    code = code_formatter()

    code(
        f"""
#ifndef __DEBUG_{name}_HH__
#define __DEBUG_{name}_HH__

#include "base/compiler.hh" // For namespace deprecation
#include "base/debug.hh"
"""
    )
    for flag in components:
        code(f'#include "debug/{flag}.hh"')
    code(
        """
namespace gem5
{

namespace debug
{

namespace unions
{
"""
    )

    # Use unions to prevent debug flags from being destructed. It's the
    # responsibility of the programmer to handle object destruction for members
    # of the union. We purposefully leave that destructor empty so that we can
    # use debug flags even in the destructors of other objects.
    if components:
        code(
            """
inline union ${{args.name}}
{
    ~${{args.name}}() {}

    CompoundFlag flag${{args.name}};

    ${{args.name}}() : flag${{args.name}}("${{args.name}}", "${{args.desc}}",
        {
            ${{",\\n            ".join(
                f"(Flag *)&::gem5::debug::{flag}" for flag in components)}}
        }) {}

} instance${{args.name}};
"""
        )
    else:
        code(
            """
inline union ${{args.name}}
{
    ~${{args.name}}() {}
    SimpleFlag flag${{args.name}};

    ${{args.name}}() : flag${{args.name}}("${{args.name}}", "${{args.desc}}", ${{"true" if fmt else "false"}}) {}

} instance${{args.name}};
"""
        )

    code(
        """
} // namespace unions

inline constexpr const auto& ${{args.name}} =
    ::gem5::debug::unions::instance${{args.name}}.flag${{args.name}};

} // namespace debug
} // namespace gem5

#endif // __DEBUG_${{args.name}}_HH__
"""
    )

    code.write(hh)


if __name__ == "__main__":
    args = parse_args()

    fmt = args.fmt.lower()
    if fmt == "true":
        fmt = True
    elif fmt == "false":
        fmt = False
    else:
        print(f'Unrecognized "FMT" value {fmt}', file=sys.stderr)
        sys.exit(1)
    components = args.components.split(":") if args.components else []

    write_header_file(args.hh, args.name, args.desc, fmt, components)
